Change the IO buffer size on Windows to 32k

Change the IO buffer size on Windows to 32k

This makes a program like this

import "dart:io";

main() {
  stdin.pipe(stdout);
}

with stdin redirected from a file run 20 - 50 times faster depending
in the file size piped through.

R=ager@google.com

BUG=

Committed: https://code.google.com/p/dart/source/detail?r=20210

[Mads Ager (google), 2013-03-19 15:11:20]

LGTM

https://codereview.chromium.org/12935002/diff/1/runtime/bin/eventhandler_win.cc
File runtime/bin/eventhandler_win.cc (right):

https://codereview.chromium.org/12935002/diff/1/runtime/bin/eventhandler_win....
runtime/bin/eventhandler_win.cc:23: #define BUFFER_SIZE 32 * 1024
Please use a constant as below.

static const int kBufferSize = 32 * 1024;

[Søren Gjesse, 2013-03-19 15:26:48]

https://codereview.chromium.org/12935002/diff/1/runtime/bin/eventhandler_win.cc
File runtime/bin/eventhandler_win.cc (right):

https://codereview.chromium.org/12935002/diff/1/runtime/bin/eventhandler_win....
runtime/bin/eventhandler_win.cc:23: #define BUFFER_SIZE 32 * 1024
On 2013/03/19 15:11:20, Mads Ager wrote:
> Please use a constant as below.
> 
> static const int kBufferSize = 32 * 1024;

Done.

[Søren Gjesse, 2013-03-19 15:27:10]

Committed patchset #1 manually as r20210 (presubmit successful).